1. Field of the Invention
The present invention relates to an irrigation system for conveying a fluid from a fluid source through interconnected spans wherein an alignment mechanism maintains alignment of the respective spans.
2. Description of the Prior Art
The irrigation system to which the present invention pertains includes a series of irrigator spans having conduits for conveying water. The primary type of irrigation system used for this purpose is called a center pivot irrigation system. Such systems include a center pivot tower about which the entire system will rotate. The center pivot tower is connected to the water source for supplying the water to the irrigation system. The irrigation system further includes a series of irrigator spans having conduits for conveying the water. Each irrigator span is connected to the adjacent irrigator span in an end-to-end manner at a joint that may include a ball and socket connection or simply a tongue and pin connection. A coupling is used to connect the conduits of adjoining irrigator spans such that each conduit is in fluid communication with the next. The conduit of the irrigator span positioned adjacent to the center pivot tower is connected to the center pivot tower and the water source. The water is pumped from the water source through the conduits of each irrigator span and is applied to the field through discharge nozzles mounted to the conduits. The irrigation system may include several irrigator spans capable of reaching tens to hundreds of acres of the field, or the irrigation system may only include only a few irrigator spans capable of reaching only a few acres. The irrigator spans are moved about the center pivot tower by a drive system. Each irrigator span includes its own drive system for moving the span radially about the center pivot tower. In prior art irrigation systems, an alignment mechanism interconnects each pair of connected irrigator spans near the joint to maintain radial alignment between the irrigator spans within a predetermined limit.
For example, U.S. Pat. No. 4,034,778 to Sage et al. granted Jul. 12, 1977 discloses an irrigation system for conveying a fluid from a fluid source. The prior art irrigation system includes a first irrigator span having a first end at a water source and extending to a distal end. A first drive system moves the first irrigator span. The first drive system may be a constant speed or variable speed drive system. A second irrigator span extends from the distal end of the first irrigator span and a second drive system moves the second irrigator span. An alignment mechanism interconnects the first irrigator span and the second irrigator span for maintaining alignment between the first irrigator span and the second irrigator span within a predetermined limit. The alignment mechanism of the ""778 patent to Sage et al. includes a strain gauge that measures the deformation of an alignment bar interconnecting the first irrigator span and the second irrigator span. An output signal is sent to the first drive system to vary the speed of the first drive system in response to flexure or strain of the alignment bar to maintain the alignment between the first and second irrigator spans. A disadvantage of the alignment mechanism used in the ""778 patent to Sage et al. is the flexure or strain placed on the alignment bar. Strain results in a weaker structural integrity and over time the alignment bar of the ""778 patent will become permanently deflected giving rise to erroneous results or constant servicing.
Similarly, U.S. Pat. No. 3,823,730 to Sandstrom et al. granted Jul. 16, 1974 discloses an irrigation system having a first and second irrigator span, a first and second drive system coupled to the corresponding irrigator spans, and an alignment mechanism. The alignment mechanism of the ""730 patent to Sandstrom et al. includes an alignment bar, but instead of a strain gauge, as in the ""778 patent to Sage et al., a potentiometer is attached to the alignment bar to measure the alignment between the first and second spans. The potentiometer sends an output signal to a control network. The control network assesses the direction of travel of the irrigation system and the alignment of the irrigation system to determine whether to send or interrupt power to the first drive system. The first drive system is a constant speed drive system and depending on the output signal sent from the potentiometer, the first drive system is activated, deactivated, or maintained in its present condition. Hence, the output signal from the potentiometer is treated as a digital signal such that one range of variable signals corresponds to a (xe2x88x921) output and a second range of variable signals corresponds to a (+1) output. The first drive system is thereby activated or deactivated in response to the (xe2x88x921) and (+1) outputs. A disadvantage of the irrigation system of the ""730 patent to Sandstrom et al. is the stress placed on the irrigation system as a result of starting and stopping (activating and deactivating) the first drive system. In addition, the first drive system requires a high rush of energy to begin motion, thus consuming a massive amount of energy while moving through the field. Consequently, water from the irrigation system is unevenly and insufficiently applied resulting in uneven crop yields. Certain areas of the field are properly irrigated and receive adequate amounts of water while other areas are underserved.
Agricultural crop production has seen incredible advances in technology over the last twenty-five years. Farmers and agribusiness men and women rely on technology to increase production and profitability of cash-crop operations. New improvements in providing weed and pest protection have played a significant role in increasing production and profitability. Accordingly, irrigation system manufacturers have struggled to develop irrigation technology that enables large cash-crop enterprises to provide water for irrigation, fertilizer, and weed and pest protection at a significant cost savings. Traditionally, crop dusters and conventional, tractor-pulled applicators are used to spray chemicals and apply fertilizers on fields. The man-hours required to spray a field using a tractor and an applicator and the cost to use a crop duster are significant.
Current irrigation technology, however, lacks the precision and ability to apply standard chemical application rates. Either the irrigation system doesn""t move fast enough to apply the standard rate, or the uneven, unbalanced movement of the irrigator system results in unevenly applied, and therefore, wasted chemicals. For instance, the typical thirteen hundred foot irrigation system disperses, at a minimum, four thousand gallons per acre, which is suitable for strictly water irrigation. However, chemicals such as fungicides require an application of between five hundred to one thousand gallons per acre. The stopping and starting motion of the irrigation system significantly slows the overall movement of the system, preventing conventional irrigation systems from being used in chemical application.
As a result, there is a need in the art for an irrigation system designed to overcome the prior art problems associated with applying water and chemicals to a field. More specifically, there is a need for a faster, continuous motion irrigation system that does not rely on straining structural members to maintain the alignment between the irrigator spans. A faster moving system would significantly improve water and chemical application precision. Furthermore, a system that does not rely on stopping and starting the drive systems to maintain the alignment within the predetermined limit could be utilized to apply weed and pest control chemicals. A faster system, combined with a uniformly moving system would be capable of applying standard chemical rates, and also provide better and more efficient water irrigation.
The present invention provides an irrigation system for conveying a fluid from a fluid source. The irrigation system includes a first irrigator span having a first end at the fluid source and extending to a distal end. A first drive system moves the first irrigator span. A second irrigator span extends from the distal end of the first irrigator span and a second drive system moves the second irrigator span. An alignment mechanism interconnects the first irrigator span and the second irrigator span to maintain alignment between the first irrigator span and the second irrigator span within a predetermined limit. The system is characterized by one of the drive systems being variable speed and the alignment mechanism including a potentiometer for measuring the magnitude of misalignment between the first and second irrigation spans for varying the speed of one of the drive systems. The speed of one of the drive systems is varied to realign the first irrigator span and the second irrigator span to maintain the predetermined limit.
The subject invention exhibits many advantages over the prior art. The primary advantage is the elimination of the need to start and stop the drive systems responsible for moving the irrigator spans to maintain the predetermined limit. The subject invention relies on the potentiometer to measure the magnitude of misalignment and to vary the speed of one of the drive systems accordingly. The present invention further provides the capability to spray chemicals such as herbicides and pesticides to a field using an irrigation system. The prior art fails to provide an irrigation system that maintains a steady pace around the field during chemical application. Furthermore, the alignment mechanism of the subject invention does not require straining any structural members interconnecting the first and second irrigator spans, resulting in a longer life and better alignment.